Conventionally, disposable diapers are known including front and rear waist regions and a crotch region extending between these front and rear waist regions wherein the crotch region is formed with an indicator adapted to detect the occurrence of urination. For example, JP 2007-175390 A (PTL 1) discloses a disposable diaper including a crotch region coated with an adhesive containing an ingredient adapted to develop color reaction in response to contact with moisture such as urine so that such an adhesive may function as an indicator.
The disposable diaper described in PTL 1 includes a liquid-absorbent body, a liquid-permeable topsheet lying on the skin-facing side of the absorbent body facing the wearer's body, i.e., the liquid absorbing surface of the absorbent body, a leakage-barrier sheet lying on the bottom side of the absorbent body and a backsheet lying on the outer surface of the leakage-barrier sheet. The absorbent body is wrapped with a wrapping sheet and the side of the leakage-barrier sheet facing the absorbent body is formed with the indicator. As a material of the core wrapping sheet, a hydrophobic fibrous nonwoven fabric is used to prevent the indicator from coming in direct contact with the absorbent body. The absorbent body intrinsically has water absorbability and may absorb moisture vapor in the atmosphere even in an unused state of the diaper. However, the absorbent body may be wrapped with the hydrophobic wrapping sheet to prevent the indicator from undergoing a color change due to moisture vapor in its unused state.